As is known, a compact disc (CD) stores digital audio data that is read by a CD player. The CD player, which may be a standalone device, such as a portable compact disc player, part of an audio system, or contained within a personal computer, renders the digital audio data into audible signals. To ensure that a CD player can play various CDs, standards have been established to prescribe the digital encoding and data rates of audio signals.
One such standard, AES3-1992,—established by the audio engineering society (AES)—provides guidelines for transmitting digital audio data over a single transmission line. In general, digital audio is serially communicated over a single transmission line in data blocks. Each data block is comprised of a plurality of frames (for example, 192). Each frame, in turn, is comprised of two preambles, two data channels, control information, and error detection information. The preambles delineate the two data channels within a frame, where the first preamble of a first frame of new block is unique to identify the beginning of the new block. The AES3-1992 further prescribes that the digital audio data is to be biphase encoded, with the preambles being violations of the biphase encoding.
The digital audio data may be transmitted at a data rate of 32 kHz, 44.1 kHz, 48 kHz, or 96 kHz, depending on the audio application. For example, digital video discs (DVD), which digitize audio in accordance with Dolby AC-3 technologies, use a 96 kHz data rate. In addition, the system clock a digital audio interface may be 256, 384, or 512 times the sampling frequency, which is selectable via control data. As such, an AES3-1992 compliant transmitter and/or receiver must be able to process digital audio at any of the data rates and using any of the selectable clock frequencies.
Therefore, a need exists for a method and apparatus for interfacing digital audio in accordance with the AES3-1992 standard.